Physiological signals include heartbeat, brainwaves, breath, body temperature, and so on. All these physiological signals are signs of health, and if the related information of the physiological signals can be obtained easily, it helps a lot to take care of patients, the labor cost can be reduced and the quality of medical care can be improved.
FIG. 1 illustrates an electrocardiogram (ECG) signal of the heartbeat. Generally speaking, the Q-S interval is called QRS wave, wherein the point of the QRS turning upwardly is point Q, the peak is point R, and the final lowest point of the QRS is called point S. In the discrimination procedure of QRS, firstly the peak inspection procedure is performed to find out QRS in the physiological signal, and then parameters such as the amplitude and duration of the QRS wave are measured, and the average value and the standard deviation of the parameters are calculated to serve as the standard template. Thereafter, each QRS wave is compared with the template.
The heart rate variability (HRV) analysis is a method of analyzing the heart's physiological function from the heartbeat interval sequence. The standard analysis procedure was defined by the European and American Heart Association in 1996 (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, 1996), and later, it was modified (Kuo et al., 1999) in some parts, and the principles are substantially illustrated as follows.                (1) First the information of the heartbeat interval is acquired mainly by defining the onset of each heartbeat from the R wave in the ECG, and the interval between each R wave and the next R wave is a heartbeat interval RR.        (2) If the significant amplitude fluctuation exists in the continuous RR sequence, for example, more than three standard deviations, it may be arrhythmias or noise. If it is arrhythmias, the subject must be warned immediately, since the life of the subject is threatened. If it is noise, the analysis technique must be improved to eliminate the noise.        (3) If the significant amplitude fluctuation does not appear in the successive RR sequence, a more exact numerical analysis is carried out on the RR sequence, which includes frequency spectrum analysis (Kuo et al., 1999) and nonlinear analysis (Kuo & Yang, 2002) etc.        
The sleep stages can be distinguished according to the brain waves, the electromyography, and the oculomotor signal. If the partition of sleep stages can be easily carried out, the prevention of many sleep-related diseases can be easily realized. The measurement of the brain waves can reveal many diseases, e.g., epilepsy and Alzheimer's disease. If the measurement of breathing signals is added, diseases of sleep breathing-related such as obstructive sleep apnea syndrome can be found. Further, if the heart rate or HRV analysis is added, the connection between sleep and high blood pressure can be comprehend. The sleep physiological signal monitor and analysis are indispensable physiological signals in clinical medicine. The popularization of the measurement of the signals is helpful in prevention, monitor and diagnosis of diseases.
Most of the apparatuses for collecting physiological signals require more than one wire. Although the signal is exact, a lot of electrical wires must be connected to the subject, and the subject cannot move under examination, so that it is time-consuming to connect the wires and inconvenient for the subject. Recently, along with the progress of science and technology, semiconductor and wireless transmission technologies have become well developed, and the miniature products for detecting physiological signals have been proposed successively. A so-called ambulatory physiological signal-collecting apparatus has been achieved that is the size of a palm. Some of the apparatuses can continuously store the physiological signals in an internal memory, and some of the apparatuses can transmit the physiological signals to a remote receiver in the form of wireless wave or the IR transmission in real time, so that the health condition of the subject can be acquired in real time outside. The technologies allow the application of the physiological signal detection to be more convenient and flexible. However, the instruments are big and too heavy, and especially, the manner of connecting the wire is too complex for persons who have no training. Although the electrical wires are short, it is also inconvenient for users. Therefore, currently, ambulatory physiological signal-collecting instruments are still used as medical instruments, and the instrument wearing must be done under the instruction of experts. Therefore, the instruments are not consumable electronic products that can be freely used by common people.
In order to spread the physiological signal analysis technology widely to each family and person, it is necessary to overcome the inconvenience of various fixed or portable physiological instruments, and miniaturization and completely wireless instruments inevitably become the direction to follow in development.